This proposal requests continued support for a program of research on young children with severe-to- profound hearing loss. The long-term goal of this project is to investigate the effects of early intervention with cochlear implants (CIs) or hearing aids (HAs) on the development of speech perception, spoken word recognition and language skills longitudinally in children with prelingual hearing loss. We will also investigate variation and individual differences in speech and language outcomes after cochlear implantation. The proposed research is organized into three subprojects. First, we will investigate spoken word recognition and language development during the first three years of life in children with congenital, severe- to-profound hearing loss who have received either CIs or HAs. Second, we will examine spoken word recognition and receptive language abilities as a function of age at time of implantation in children who all are implanted prior to 3 years of age. Third, we will explore the benefits of CIs in children who present with handicapping conditions in addition to hearing loss. The proposed research should provide important new knowledge about the effectiveness of CIs in very young children who are representative of the current population of pediatric Cl recipients - children with severe-to-profound hearing loss identified through universal newborn hearing screening who are implanted prior to age 3 years. Such information will help to inform decisions regarding the medical and audiological management of infants and children with hearing loss. Furthermore, these projects are theoretically important because they examine the consequences of early auditory deprivation and early linguistic experience after implantation on the development of speech perception, spoken word recognition and language abilities.